The conclusion may be in any form that the sense allows.
I. Present Condition, Non-committal
- If this pebble is a diamond, {it is valuable. | guard it carefully. | you have made a great discovery. | you will get a large sum for it. | why are you so careless of it? | what a prize it is!}
- If it is raining, shut the window.
- If Jack lives in this house, {he is a lucky boy. | ring the bell. | he has moved since last May.}
II. Past Condition, Non-committal
- If that pebble was a diamond, {it was valuable. | why did you throw it away? | go back and look for it.}
- If Tom has apologized, {he has done his duty. | you ought to excuse him. | forgive him.}
If John had reached home before we started, he must have made a quick journey.
In each of these examples, the speaker declines to commit himself as to the truth of the supposed case. Perhaps the pebble was a diamond, perhaps not; Tom may or may not have apologized; whether or not John had reached home, we cannot tell.
423. In a condition contrary to fact, the if-clause takes the past subjunctive when the condition refers to present time, the pluperfect subjunctive when it refers to past time.
The conclusion regularly takes should or would ([§ 286, 3]).
- If John were here, I should recognize him. [Present condition, present conclusion.]
- If John were here, I should have recognized him before this. [Present condition, past conclusion.]
- If I had offended him, I should have regretted it. [Past condition, past conclusion.]
- If I had then offended him, I should regret it now. [Past condition, present conclusion.]